Note: Descriptions are shown in the official language in which they were submitted.
~ ~ 3 ~
T~ERMALLY P~O~ ABLE IMAGING ~L~M~NT
C~MP~ISING AN OVERCOAT LA~ER
Thi~ invention relate~ to a thermally
processable imaging element comprising a hydrophobic
imaging layer and a hydrophilic overcoat layer with
an adhesion promoting layer between the imaging layer
and the overcoat layer that promotes adhe~ion of ~he
overcoat layer without adversely affecting
sensitometric properties of the imaging element.
Thermally processable ima~ing elements,
including films and papers, for producing images by
thermal processing are known. These elements include
photothermographic elements in which an image is
formed by imagewise e~posure to light followed by
development by uniformly heating the element. These
elements also include thermographic elements in
which an image is formed by imagewise heating the
element. Such element~ are described in, ~or
example, ~Qsçarch ~i~lQ~ure~ June 1978, Item No.
17029; U.S. Patent 3,457,075; U.S. Patent 3,933,508;
U.S. Patent 3,0~0,254 and U.S. Patent 4,741,992.
Overcoat layers have been useful on the
thermally processable imaging element~ to prevent
undesired marking of the element during processing
and hinder or prevent release o~ ~olatile components
from the element at processing temperatures. An
e~ample of such an overcoat is a gelatin overcoat. A
gelatin overcoat has not been effective to prevent
migration of volatile components, such as succin-
imide, during long storage and at higher humidityduring thermal proces R ing.
An example of an effective overcoat is
described in U.S. Ratent 4,74~,992. Such an overcoat
comprises polytsilicic acid), particularly poly
(silicic acid) in combination with a hydrophilic
mo~omer or polymer, euc~ as poly(vinyl alcohol).
This overcoat however has not been entirely
--2--
aatisfactory ~hen the thermally proceRsable imaging
element comprises an imaging layer that i8
hydrophobic, such an imaging layer comprising a
poly(vinyl butyral) binder. I~ has been desirable to
increase the degree o adhesion of such an oYercoat
to a imaging layer, particularly an imaging layer
that i8 hydrophobic, to reduce the tendency or
prevent the overcoat layer from being removed or
being distorted during thermal proces~ing. None of
the above art suggests an answer tha~ meets the
requirements of such a thermally imaging element,
particularly ~ithout adversely affecting the
sensitometric properties of the element.
Polymers that have been considered to
provide improved adhesion to layers on a support have
not sati~fied the requirements of a thermally
processable imaging element because the polymers
either ha~e not provided the required degree of
adhesion or have provided such adverse effectg as
poor barrier for volatile components, Quch as
succinimide, during heat processing. Examples of
such unsatisfactory polymer~ are poly(vinyl alcohols)
such as disclosed in U.S. 4,741,992.
It has been found that the described
requirements are satisfied by a thermally processable
imaging element comprising a support bearing a
thermally processable hydrophobic imaging layer and,
on the side of the imaging layer away from the
support, an overcoat layer comprising poly(silicic
acid) and a hydrophilic monomer or polymer, wherein
the element comprises a polymeric adhesion promoting
layer between the overcoat and the imaging layer.
The polymeric adhesion promoting layer compri8es a
polymer that not only adheres well to the hytrophobic
imaging layer but al80 adheres well to the
hydrophilic overcoa~ layer.
2~33~
-3-
Such polymers that are useful in the
polymeric adhesion promoting layer are:
1) terpolymers o~ 2-propenenitrile,
l,l-dichloroe~hene, and prope~o~c acid,
~uch a8 disclosed in U.S. 3,271,345; and
2) terpolymers of 2-propenoic acid, methyl
e~ter, l,l-dichloroethene and itaconic
acid aR disclosed in, for example, U.S.
3,437,484.
Combinations of such polymers in the
polymeric adhesion promoting layer are also useful.
Such polymeræ are represented by the
formulas:
15 1) ¦ CH2=C~-CN ¦ ¦ C~2=CC12 ¦ ¦ C~2=CH~COOH ¦ and
x y z
¦_CE12 C~--CO--OCH3 ¦ ¦ C~2=CCl 2
q r
I C~2=C(C00~)-C~2C00~ 1
s
wherein x, y, z, q, r and s are individually integers
that enable a molecular weight of polymer that forms
a coatab~e composition.
These polymers can be prepared by methods
:: known in the polymer ~ynthesis art. For e~ample,
terpolymers of 2-propenenitrile, l,l-dichloroethene
and propenoic acid are prepared by copolymerizing the
respective monomers by polymerization methods known
in the polymer art. These methods include known
: emulsion a~d solution polymeriæation methods.
A u$eful polymeric adhesion promoting layer
: composition a~ coated on the imaging layer does not
adversely ~low, ~mear or dihtort at proce~sing
temperature6 of the element, typically within the
range of 100C to 200C.
-4-
The optimum concentration of adhesion
promoting polymer in the polymeric adhe~ion promotin~
layer will depend upon such factors as ~he particular
components of the adhesion promoting layer, the
particular adhesion promoting polymer, the particular
thermally processable element, and proces~ing
conditions. Typically the concentration o~ adhesion
promoting polymer is present in the polymeric
adhecion promoting layer within the range of 30 to
99% by weight o~ ~he layer. A preferred
concentration of adhesion promoting polymer is within
the range of 60 to 99% by weight of the layer.
A useful polymeric adhesion promoting layer
i8 typically transparent and colorless. The overcoat
layer on the adhesion promoting layer is also
typically transparent and colorless. If the~e layers
are not transparent and colorless, then it is
necessary, if the element is a photothermographic
element, that the layers be at leaæt transparent to
20 the ~avelength of radiation employed to provide and
view the image. The polymeric adhesion promoting
layer and the overcoat do not significantly adversely
effect the imaging properties, such as the
sensitometric properties of the photothermographic
element.
Other components, particularly other
polymers, can be useful in the polymeric adhesion
promoting layer and/or the overcoat layer. Other
components that can be useful in one or the other or
both of the~e layers include such other polymers as
~ater-soluble hydroxyl containing polymers,
preferably poly(vinyl alcohol), or monomers that are
compatible with the polymers of the~e layers. Other
component~ that can be pre~ent in these layers
include, for example, ~urfactants, ~tabilizers and
matting agents.
~ 3
-5-
Imaging element~, particularly
photothermographic or thermographic elements, as
deQcribed can comprise, if desired, multiple overcoat
layers and/or multiple polymeric adhesion promoting
layers. For example, the imaging element can
comprise on the imaging layer a fir~t polymeric
adhesion promoting layer, a first overcoat
compri~ing, for e~ample, a water-soluble cellulose
derivative, ~uch as cellulose acetate, and a second
overcoat comprising poly(silicic acid) and poly(vinyl
alcohol).
The polymeric adhesion promoting layer is
useful on any thermally processable imaging element,
particularly any photothermographic or thermographic
element that has an imaging layer with which the
polymeric adhesion promoting layer is compatible.
The thermally proces~able imaging element can be a
black and white imaging element or a dye-forming
thermally processable lmaging element. The polymeric
adhesion promoting layer is particularly useful on an
imaging layer of a photothermographic element
designed for dry physical development. ~seful silver
halide elements on which the polymeric adhesion
promoting layer is useful are described in, for
example, U.S. Patent Nos. 3,457,075; 4,459,350;
4,264,725; and ~esearch Di~clo~ure, June 1978, Item
No. 17029. The polymeric adhesion promoting layer is
particularly u~eful on, for example, a
photothermographic element comprising a support
bearing, in reactive association, in a binder,
particularly a poly(vinyl butyral) binder, ~a)
photographic ~ilver halide, prepared in situ and/or
ex situ, (b) an image forming combination comprising
(i) an organic silver ~alt oxidizing agent,
preferably a silver salt of a long chain fa~ty acid,
such as silver behenate, with (ii) a reducing agent
for the organic silver ~alt oxidizing agent,
--6--
preferably a phenolic reducing agent, and (c) an
optional toning agent, 8uch as succinimide. The
photothermographic element preferably ha~ directly on
the polymeric adhesion promoting layer an ov~rcoat
layer, preferably an o~ercoat layer comprising 50 to
90% by weight o~ the overcoat layer of poly(silicic
acid) and 1 to 50% by weight of the overcoat layer of
poly(vinyl alcohol).
A particularly preferred embodiment is a
photothermsgraphic element comprising a ~upport
bearing, in reactive as~ociation, in a binder,
particularly a poly~vinyl butyral) binder, (a)
photographic silver halide, prepared in situ and/or
ex situ, (b) an image forming combination comprising
(i) silver behenate, with (ii) a phenolic reducing
agent for the silver behenate, (c) a toning agent,
such as succinimide, and an image ~tabilizer, such as
2-bromo-2-(4-methylphenylsulfony)acetamide; and
having thereon a polymeric adhesion promoting layer
comprising at least 30% by weight of the adhesion
promoting layer of poly(2-propenenitrile-co-
1,1-dichloroethene-co-2-propenoic acid) and having on
the polymeric adhesion promoting layer an overcoat
layer comprising 50 to 90% by weight of the overcoat
layer of poly(silicic acid) and 1 to 50% by weight of
the overcoat layer of poly(vinyl alcohol),
particularly water-soluble poly(vinyl alcohol) that
is 80 to 90% hydrolyzed.
The optimum polymeric adhesion promoting
layer thickness and the optimum overcoat layer
thickness depend upon variou6 factore, such as the
particular element, proces~ing conditions, thermal
processin~ means, de~ired image and the particular
components of the layers. A particularly use~ul
layer thickness o~ the polymeric adhesion promoting
layer i8 within the ra~ge of 0.04 to 2.0 ~icron~,
preferably within the range of 1.0 to O . 05 micronB .
2~ 3
--7--
A particularly useful layer thickness of the overcoat
is within the range of 0.5 to 5.0 microns, preferably
within the range of 1.0 to 2.0 microns.
The photothermographic element comprises a
5 photosensi~ive component that consists essentially of
photographic silver halide. A preferred
concentration of photographic silver halide i~ within
the range o~ 0.01 to 10 moles of photographic ~ilver
halide per mole o~ organic silver salt oxidi~ing
10 agent, such as per mole of æilver behenate, in the
photothermographic material. Other photoæensitive
silver saltæ are useful in combination with the
photographic æilver halide if desired. Preferred
photographic silver halides are silver chloride,
silver bromide, silver bromoiodide, silver
chlorobromoiodide and mixtures of these silver
halides. Very fine grain silver halides are
especially useful. The photographic silver halide
can be prepared by any of the procedures known in the
20 photographic art. Such procedures for forming
photographic silver halide and the forms of silver
halide are described in, for example, ~e~earch
Disclosure, June 1978, Item 17029 and R~eax~h
DiscloRure, December 1978, Item No. 17643. Tabular
grain photographic silver halide is also useful, as
described in, for example, U.S. Patent No.
4,435,499. The photographic ~ilver halide can be
waæhed or unwashed, chemically sensitized, protected
again~t the production of fog and stabilized against
30 the los~ of sen~itivity during keeping aæ described
in the above Research Disclosure publicatio~s. The
silver halides can be prepared in situ, such as
described in U.S Patent No. 3,457,075, or prepared ex
situ by procedures known in the photographic art.
The photothermographic element typically
compriseæ an oxidation-reduction imaging forming
combination that contains an organic silver salt
2 ~1 :1 .3 3 :~ ~
oxidizing agent, preferably a silver salt of a long
chain fatty acid. Such a silver ~alt of a long chain
fatty acid i8 resistant to darkening upon
illumi~ation. Preferred organic silver 8alt
.5 oxidizing agents are sllver ~alts of long chain fatty
acids that contain 10 to 30 carbon atoms. E~amples
of such organic silver salt oxidizing agent~ are
silver behena~e, silver stearate, silver oleate,
silver laurate, silver hydroxystearate, silver
10 caprate, silver myri~tate and silver palmi~ate.
Combination~ of organic silver salt oxidizing agents
are also useful. Examples of useful silver salt
oxidizing agents that are not silver salts of long
chain fatty acids include, for example, silver
benzoate and silver benzotriazole.
The optimum concentration of organic silver
salt oxidizing agent in a photothermographic element
will vary depending upon the desired image,
particular silver salt oxidizing agent, particular
reducing agent, and particular photothermographic
element. A preferred concentration of silver salt
oxidizing agent is within the range o~ 0.4 to 100
moles of organic silver salt oxidizing agent per mole
of sil~er. When combinations o~ organic silver salt
oxidizing agent are present, the total concentration
of organic silver salt oxidizing agent i~ preferably
within the described concentration range.
A variety of reducing agents are useful in
the photothermographic element. Examples of useful
reducing agents include ~ubstituted phenols and
naphthols such as bis-beta-naphthols; polyhydroxy-
benzenes, such as hydroquinones, catechols and
pyrogallols; aminophenols, such as 2,4-diaminophenols
and methylaminophenols; ascorbic acid reducing
agents, such as ascorbic acid, ascorbic acid ketals,
and other ascorbic acid derivatives; hydro~ylamine
reducing agents; 3-pyrazolidone reducing agents, ~uch
2~3
~9_.
as l-phenyl-3-pyrazolidone, and 4-methyl-4-hydroxy-
methyl-3-pyrazolidone; sulfonamidophenol~ and other
organic reducing agents a~ de~cribed in, for e~ample,
U.S. Patent 3,933,508 and Re6earch i~clo~ure, June
5 1978, Item No. 17029. Combination~ of organic
reducing agents are also useful.
Preferred organic reducing agents in
photothermographic elements as described are
sulfonamidophenol reducing agents, such as de~cribed
10 in U.S. Patent 3,801,321. Examples of useful
sulfonamidophenols include 2,6~dichloro-4-benzene-
sulfonamidophenol; benzenesulfonamidophenol;
2,6-dibromo-4-benzenesulfonamidophenol and mixtures
of such ~ulfonamidophenols.
An optimum concentration of reducing agent
in a photothermographic element as described varies
depending upon such factors as the particular
photothermographic element, desired image, processing
conditions, the particular silver salt oxidizing
20 agent and other addenda in the element. A preferred
concentration of reducing agent is within the range
of about 0.2 mole to about 2.0 moles of reducing
agent per mole of silver in the photothermographic
element. When combinations of reducing agents are
25 present, the total concentration of reducing agent is
preferably within the described range.
The photothermographic element preferably
comprises a toning agent, al80 kno~n as an
activator-toner or a toner-accelerator. Combinations
30 of toning agents are al~o useful in the
photothermographic element. An optimum toning agent
or combination of toning agents depend~ upon such
factors as the particular photothermographic element,
desired image, particular component3 in the imaging
35 material, and proces~ing conditions. E2amples of
useful toning agent~ include phthalimide,
N-hydroxyphthalimide, N-pota~sium phthalimide,
10--
succinimide, N-hydroxy-1,8-naphthalimide, phthala-
zine, 1-(2~)-phthalazinone, and 2-acetylphthalazinone.
Stabilizers that are u~eful in photothermo-
graphic element~ include photolytically acti~e
5 ~tabilizers and stabilizer precursors as described
in, ~or example, U.S. Patent No. 4,459,350 and
include, for example, aæole thioethers and blocked
azolinethione stabilizer~ and carbamoyl ~tabilizer
precursors such as described in U.S Patent 3,877,940.
Photothermographic materials as described
preferably contain various colloids and polymers
alone or in combination as vehicles and binding
agents and in various layers. U~eful vehicles and
binding a~ents are hydrophilic or hydrophobic. They
15 are transparent or tran~lucent and include naturally
occurring substances, such as gelatin, gelatin
derivatives, polysaccharides, such as dextran, gum
arabic, cellulose derivatives and the like; and
~ynthetic polymeric ~ubstances such as water-soluble
20 polyvinyl compounds, for example poly(vinyl-
pyrrolidone) and acrylamide polymers. Other
synthetic polymeric compounds that are u~eful include
dispersed vinyl compounds such as in latex form and
particularly those that increase dimen~ional
25 stability of photographic materials. Effective
polymers include water insoluble polymers of
alkylacrylates and methacrylate~, acrylic acid,
sulfoalkylacrylates and tho~e that have cross-linking
sites that facilitate hardening or curing. Preferred
30 high molecular weight materials and resins that are
u~eful as binders and vehicles include poly(vinyl
butyral~, cellulose acetate, poly(methyl-
methacrylate), poly(vinylpyrrolidone), ethyl
cellulose, polystyrene, poly~vinylchloride),
35 chlorinated rubbers, polyisobutylene, butadiene-
~tyrene copolymers, vinyl chloride vinyl acetate
copolymers, copolymer~ of vinyl acetate and
~:9 3~ ~ ~
vinylidene chloride, poly(vinyl alcohol), and
polycarbonate~.
Photothermographic mat@rial~ can contain
development modifiers that function as ~peed
increasing compounds, sensitizing dye~, hardener~,
antistatic layers, plasticizer6 and lubricants,
coating aids, bri~hteners, absorbing and filter dyes,
such as described in Research Dis~losure, December
1978, Item No. 17643 and Research Di3cloaure, June
197g, Item No. 17029.
The thermally processable elements comprise
a variety of supports. Examples o~ useful supports
include poly(vinylacetal) film, polystyrene film,
poly(ethyleneterephthalate) film, polycarbonate film
and related ~ilms and resinous materials as well as
glass, paper, metal and other supports that can
withstand the thermal proces3ing temperatures.
The layers, including the imaging layers,
the adhesion promoting layer, and overcoat layers, of
a thermally processable element as described can be
coated on the ~upport by coating procedures known in
the photographic art, including dip coating, air
knife coating, curtain coating or extrusion coating
u~ing ~oppers. If desired, two or more layer3 are
coated simultaneously.
Spectral ~ensitizing dyes are useful in the
described photothermographic material~ to confer
added sen~itivity to the elements and compositions.
Useful sen~iti~ing dyes are de~cribed in, for
example, the above Re~arch ~isclo~u~e publications.
A photothcrmographic material preferably
comprises a thermal stabilizer to help ata~ilize the
photothermographic material prior to egposure and
processi~g. Such a thermal stabilizer aids
improvement of ~tability o~ the photothermographic
material during storage. Preferred thermal
~tabilizers are (a) 2-bromo-2-arylsulfonylacetamides,
-12-
such as ~-bromo-2-p-toly~ulfonylacetamide, (b)
2-(tribromomethylsulfonyl)benzothiazole and (c)
6-substituted-2,4-bi~(tribromomethyl)-s-triazine,
such as 6-methyl or 6-phenyl-2,4-bis(tribromo-
methyl)- 8 - triazine.
The thermally processahle element~ are
e~posed by means of various forms of energy in the
case of silver halide photothermographic elements.
Such forms of energy include those to which the
photosensitive silver halide i~ sensitive and include
the ultra~iole~, visible, and infrared regions of the
electromagnetic spectrum as well as electron beam and
beta radiation, gamma ray, x-ray, alpha particle,
neutron radiation and other forms of corpuscular
wave-like radiant energy in either non-coherent
(random-phase) or coherent (in-phase) ~orms as
produced by lasers. Exposures are monochromatic,
orthochromatic or panchromatic depending upon the
spectral sensitization of the photographic silver
halide. Imagewise exposure i3 preferably for a time
and intensity sufficient to produce a developable
latent image in the photothermographic material.
After imagewise expo~ure of the photothermographic
material, the resulting latent image i8 developed
merely by overall heating the element at moderately
elevated tempera~ure~. This o~erall heating merely
involves heating the element to a ~emperature within
the range of about 90C to 150C until a developed
image i 8 produced, such as within about 0.5 to about
60 ~econds. By increasing or decrea3ing the thermal
processing temperature a shorter or longer processing
time is useful depending upon the desired image, the
particular components in the photothermographic
material and the heating means. A preferred
processing tempera~ure i8 within ~he range of about
100C to about 130C.
2 ~
In the case of thermographic elements the
thermal energy ~ource and means for imaging purposes
can be any imagewise thermal exposure source and
means that are known in ~he thermographic art. The
imagewise heating means can be, for example, an
infrared heating means, la~er, microwave heating
means or the like.
Heatin~ mean~ known in the photothermo-
graphic and thermographic art can be used for
providing the desired thermal processing temperature
range for processing the photothermographic element.
The heating means can be, for example, a simple hot
plate, iron, roller, heated drum, microwave heating
means, or heated air.
Thermal processing i8 preferably carried out
under ambient conditions of pressure and humidity.
Conditions outside normal atmospheric pressure and
humidity are useful if desired.
The eomponents of the thermally processable
element can be in any location in the element that
provides the de~ired image. If desired, one or more
of the components of the photothermographic element
can be in on or more layers of the element. For
example, in some cases, it i~ desirable to include
cer~ain percentage3 of the reducing agent, toner,
stabilizer precurRor and/or other addenda in the
adhesion promoting layer and/or in the overcoat layer
of the photothermographic element.
It is neces3ary that the component of the
imaging combination be "in association" with each
other in order to produce the desired image. The
term "in association" herein means that in the
photothermographic element the photo~ensitive ~ilver
halide and the image-forming combination are in a
location ~ith respect to each other that enables the
desired procesæing and produces a useful image.
~3
-14-
Thermographic elements on ~hich the adhesion
promoting layer and the overcoat layer are useful
include any that are compatible with the polymer that
comprises the adhesion promoting layer. Such
photothermographic elements include tho~e deacribed
in, for example, U.S. Patent Nos. 2,663,657;
2,910,377; 3,028,254; 3,031,329 and 3,080,254. An
example of a useful thermographic element compriges a
~upport bear ing a thermographic imaging layer having
thereon an adhesion promoting layer as described and
thereon an overcoat layer, al~o as de~cribed.
The term water-soluble herei~ means at least
2 grams of the compound or composition dissolves in
one liter of water within 2 hours at 90C.
The following examples further illu~trate
the invention.
Example 1:
This illustrates use of poly(2-propeneni-
trile-co~l,l-dichloroethene-co-2-propenoic acid~
designated herein as Terpolymer No. 1 in an adhesion
promoting polymer layer in a photothermographic
element between a hydrophobic imaging layer and an
overcoat layer.
A photothermographic element waQ prepared
having the following photothermographic layer on a
blue poly(ethylene terephthalate) film ~upport:
I. Photothermographic Emulsion L~yer (designated
herein as the E-Layer):
Pho~othermographic Laver m~/ft
Silver Behenate (Ag) 80.0
HgBr2 (Hg) 0.1
AgBr (Ag) 40.0
NaI 3.5
Succinimide toner/development modifier 42.0
Surfactant (SF-96 which is a polysiloxane l.S
fluid and i8 available from and a trademar~
of General Electric Co., U.S.A.)
-lS-
M~obromo sta~ilizer: 6.0
O Br O
CH --o~
Naphthyltriazine stabilizer: 6.0
C13C\ ~N\ /CC~8
I~ ,0~ ~I
Poly(vinyl butyral) binder (Butvar B-76 a 400.0
trademark of the Monsanto Co ., U . S . A . )
Sensitizing dye 0.5
Benzenesulonamidophenol ~eveloping agent.: 100.00
HO-~ N~S02~
O--. .=.
MIBK solvent 30.0
The following layers were coated on the
E-Layer as described in following Part A and Part B:
II. Overcoat $1 ~ela$in:
Photographic gelatin 161. O
Matte 10.0
Formaldehyde 4.2
Surfactant ~Surfactant lOG which i~ ~- 4.7
isononylphenoxypolyglycidol, a trademark
of and available from the Olin Corp., U.S.A.)
III. Overcoa~ #2 - Poly(~ilicic acid~ (PSA)/Poly(vinyl
alcohol~ (PV~):
Ratio ~(Q~I~4 = 1. 25
3 5 PVA
8% PVA, Elvanol 52/22 125 . O g
Distilled Water 48 . 5 g
PSA solution 76 . 5 g
TOTAL 250 . O g
16-
Solution Of Poly(vinyl~ hol~(PVA)
An aqueous solution of 8% by weight
poly(vinyl alcohol) in water was prepared.
(8% by weight ELVANOL52/22 in water.
ELVANOL 52/22 is a trademark of ~.I. tuPont
deNemours, U.S.A.)
Solution of Poly(silicic acic~(P~A)
Xydrolysis of tetraethyl orthosilicate
(T~OS) to form poly(silicic acid)(PSA)
The following components were mixed in the
following order:
Distilled Water 144 g
lN-~-Toluenesulfonic Acid 36 ~
Ethyl Alcohol 200 g
TEOS 208 g
A clear solution of PSA was obtained in less
than 10 minutes.
IV. ~dhesion Promoting Layer:
Adhesion Promoting Layer #1:
Terpolymer #1 (30% Latex) 1 part
Distilled Water 9 partæ
Surfactant (Surfactant lOG~ 1 drop
Adhesion Promoting Layer ~2
(Terpolymer #l with PVA)
Terpolymer #1 Latex (30% solids) 10 g
2% PVA ~olution 90 g
Olin lOG Surfactant 1 drop
: 35 PVA = Poly(vinyl alcohol), ELVANOL 52l22
:~ ,
-17-
Part A: Adhesion Promoting Layer to Improve Overcoat
Adhesion:
Pho~othermographic films were prepared by
preparing ~tructures A (Comparison) and B ~I~vention):
;~
(Compar~Qa (Inven~on~
PSA/PVA (Overcoat #2PSA/PVA (Overcoat #2)
-
E-Layer Adhesion Layer*
_
E-Layer
Film Support _
Film Support
The adhesion promoting layer in B was hand-
coated at 2 mil wet laydown on top of the E-Layer
and, after drying, overcoated with the PSA/PVA
composition. Coatings A and B were tested for the
overcoat adhesion using 3M-Scotch 600 Transparen~
Tape. Overcoat i8 easily stripped off the structure
A, but not from structure B, even when the overcoat
is heavily scored prior to the tape test.
Tape test procedure: (a) Place approxi-
mately 2 i~ch strip of tape on top of the coating and
~mooth out to assure uniform adhesion to the test
æurface; (b) rip o~f the tape a~d inspect the
surface. A more drastic ~est for the o~ercoat
adhesion i~ when the overcoat is heavily scored prior
to tape application.
~art B: Comparison of Adhesion Promoting Layers and
Overcoats:
A photothermographic ~ilm a~ deqcribed in
Example 1 ~as prepared with a~ E-Layer (I) and was
overcoated with either gelatin (II) or PSA/PVA
~33~L~
overcoat (III). Selected coatings contained the
compositions and the resulting adhesion tests are
tabulated as ~ollows:
Adhesion AdheBiQ~
S ~_omoting Tape &
Layer Overco~t Tape A Tape ~ ~o~
None #2 PSA/PVA
(Control~
No. 1 #2 PSA/PVA + +
(Terpolymer
10 No. 1)
No. 2 #2 PSA/PVA + + +
(Terpolymer
No. 1 with
PVA)
15 None #l Gelatin
(Control)
No. 1 #l Gelatin + + +
(Terpolymer
No. 1)
No. 2 #1 Gelatin -*
20 (Terpolymer
No. 1 with
PVA )
* failure probably due to incompatibility of
gelatin and the poly(vinyl alcohol~ (PVA)
5 Tape A - 3M, Scotch Tape #810 (Trademark of 3M Co.,
U.S.A.)
Tape B - 3M, Transparent Tape #600
+ = pass
- = fail
The above tabulated results are qualitative
observations. These samples were also submit~ed ~or
a standard quantitative adhesion evaluation. The
results are tabulated as follows:
-19-
Adhesive P~el Force Test
Adhesion
P~omQti~ Peel Force
~ayer Q~ Gram~ cm
5 None #2 PSA/PVA 8
(Control)
No. 1 ~2 PSA/PVA 59
(Terpolymer
No. 1)
No. 2 #2 PSA/PVA>600
10 (Terpolymer
No. 1 with
PVA)
None #1 Gelatin 11
(Control)
1~ No. 1 #1 Gelatin>600
(Terpolymer
No. 1)
No. 2 #l Gelatin 33
(Terpolymer
No. 1 with
PVA)
The above examples illustrate a surprising,
significant increase in the adhesion of hydrophilic
overcoats such as gelatin or PVA/PSA to a hydro-
phobic, particularly a photothermographic E-Layer as
described.
The invention has been described in detail
with particular reference to pre~erred embodiments
thereof, but it will be understood that ~ariations
and modifications can be e~fected within the 8pirit
and scope of the invention.
